1. Field of the Invention
The present invention relates to a brightness compensation method and a local dimming circuit and a liquid crystal display thereof, and more particularly, to a brightness compensation method and a local dimming circuit and a liquid crystal display thereof which can compensate intensity loss of both local dimming and backlight scanning, to display a normal image.
2. Description of the Prior Art
In general, with a local dimming technique, different backlights corresponding to different display areas on a liquid crystal display (LCD) can be turned on with different intensity according to an image data required to be displayed, to save power consumption.
For example, if an image data includes a brighter image in a display area and a darker image in another display area, with a local dimming technique, a cold cathode fluorescent lamp (CCFL) or a light emitting diode (LED) utilized as a backlight of the display area may be controlled to turn on with a brighter backlight intensity, and those of the another display area may be controlled to turn on with a darker backlight intensity. Therefore, in comparison with the total backlights turned on with maximum backlight intensity under a normal operation, power consumption can be saved if a local dimming technique is applied.
In such a condition, since performing the local dimming technique may reduce backlight intensity of parts of the display areas in the LCD, in order to prevent a user from being influenced by the intensity loss, the conventional local dimming technique further increases image intensity, i.e. degree of liquid crystal is polarized for light emission, of the image data for compensated and then displays the image, i.e. compensates the reduced backlight intensity by increasing image intensity, so as to prevent a user from feeling that the displayed image is darker.
On the other hand, in the prior art, the local dimming technique may also be implemented together with a backlight scanning technique. With the backlight scanning technique, the display areas other than those where images are currently displaying are optionally turned off, i.e. when the LCD scans pixels for displaying, only the backlights of the display areas in which image are displaying should be turned on, so as to further save power consumption.
However, the conventional local dimming technique reduces the backlight intensity of parts of the display areas, and then performs brightness compensation with the assumption that total backlights are turned on all the time. The intensity loss caused by optionally turning off parts of the display areas with the backlight scanning technique is not considered. Therefore, when the local dimming technique is implemented together with the backlight scanning technique, the user may still feel that the displayed image is darker. Thus, there is a need for improvement of the prior art.